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Electron-phonon coupling in quasi free-standing graphene

Quasi free-standing monolayer graphene can be produced by intercalating species like oxygen or hydrogen between epitaxial graphene and the substrate crystal. If the graphene is indeed decoupled from the substrate, one would expect the observation of a similar electronic dispersion and many-body effects, irrespective of the substrate and the material used to achieve the decoupling. Here we investigate the electron-phonon coupling in two different types of quasi free-standing monolayer graphene: decoupled from SiC via hydrogen intercalation and decoupled from Ir via oxygen intercalation. Both systems show a similar overall behaviour of the self-energy and a weak renormalization of the bands near the Fermi energy. The electron-phonon coupling is found to be sufficiently weak to make the precise determination of the coupling constant lambda through renormalization difficult. The estimated value of lambda is 0.05(3) for both systems.